1. Technical Field
The present disclosure relates to an ultrasonic pipe measurement apparatus.
2. Related Art
An ultrasonic pipe measurement apparatus is an apparatus employs an ultrasonic wave to measure a generation point and size or amount of such as the damage occurred by corrosion or erosion in the pipe and scale attached to the inside of the pipe (that is, the conditions of a pipe). As an apparatus for detecting and measuring corrosion and erosion in a pipe, an ultrasonic thickness meter has been known. The ultrasonic thickness meter measures the wall thickness of a pipe using the propagation time of ultrasonic waves to measure the thickness loss due to corrosion or erosion.
FIG. 8 is a diagram illustrating an exemplary structure of the ultrasonic thickness meter (JP-A-2000-329751). As illustrated in FIG. 8, this ultrasonic thickness meter includes a piezoelectric ultrasonic transducer 1, an ultrasonic transceiver 2, a signal processing device 3, and an ultrasonic waveform display device 4 such as an oscilloscope.
The signal processing device 3 performs, for example, the calculation of the attenuation rate of the ultrasonic multiple echoes, the calculation of the amplification ratio between the incident ultrasonic echo and the reflection ultrasonic echo, and the signal processing for improving the SN ratio of a multiple reflection echo signal. Note that the pipe to be inspected has a pipe main body 5 made of iron or stainless steel. The inner surface of the pipe main body 5 is provided with a plastic or rubber lining 6. A fluid (couplant) 10 suppresses the reflection of the ultrasonic wave on the surface of the pipe main body 5.
In such a structure, an ultrasonic echo 7 is introduced into the pipe main body 5 through the outer surface thereof to detect an ultrasonic echo 8 from the lining 6 and the inner surface of the pipe main body 5. Thus, the separation between the pipe main body 5 and the lining 6 can be detected.
FIG. 9 is a diagram illustrating an exemplary structure of an apparatus for detecting the corrosion and erosion of the pipe by using a guide wave (JP-A-2005-10055). As illustrated in FIG. 9, a guide wave transceiver 11 is a device that generates a guide wave 18 in a pipe 19 and includes, for example, a piezoelectric element. The guide wave transceiver 11 is disposed in contact with the pipe 19, and is electrically connected to a guide wave transceiver unit 13 through a coaxial cable.
A transceiver ring 12 is a jig for annularly holding a plurality of guide wave transceivers 11 around the pipe. The transceiver ring 12 preferably includes a structure configured to house the guide wave transceivers 11 at equal intervals in a circumferential direction and a structure detachable from the pipe. The transceiver ring 12 has a ring-shaped frame with a structure that can be divided into two. In other words, the ring-shaped frame can be assembled by cutting a ring-shaped component into two divided pieces along the diameter of the ring and connecting the ends of the respective divided pieces together using a screw. Thus, as the divided pieces are connected together to surround the outer periphery of the pipe 19, the transceiver ring 12 can be attached around the outer periphery of the pipe 19.
On the inside of the ring-shaped frame of the transceiver ring 12, the plurality of guide wave transceivers 11 are housed. Moreover, the inside of the ring-shaped frame is supported by a spring that extends or contracts relative to the outer peripheral surface of the pipe 19. Therefore, upon the attachment of the transceiver ring 12 to the outer peripheral surface of the pipe 19, the spring presses the plurality of guide wave transceivers 11 are against the outer peripheral surface of the pipe 19. Thus, the guide wave transceivers 11 can easily generate the guide wave 18 to the pipe 19.
The guide wave transceiver unit 13 applies a transmission waveform to the guide wave transceiver 11 to transmit the guide wave 18. Moreover, the guide wave transceiver unit 13 amplifies the reception waveform from the guide wave transceiver 11. The guide wave transceiver unit 13 is connected to a waveform generation/analysis unit 15 to enable the communication of digital data. The guide wave transceiver unit 13 is connected to an A/D converter 14 through the coaxial cable for transmitting a reception waveform to the A/D converter 14.
The A/D converter 14 has a function to convert an analogue signal into a digital signal. The A/D converter 14 is connected to the guide wave transceiver unit 13 and the waveform generation/analysis unit 15. Thus, the A/D converter 14 is able to convert the reception waveform of the guide wave 18 output from the guide wave transceiver unit 13 into the digital waveform to communicate with the waveform generation/analysis unit 15.
The waveform generation/analysis unit 15 generates the transmission waveform and analyzes the reception waveform, while controlling the entire operation of a pipe inspection apparatus. The waveform generation/analysis unit 15 includes a computer or the like. The waveform generation/analysis unit 15 is connected to an input unit 16 such as a keyboard that accepts the instruction from a user, and to a display unit 17 such as a CRT.
In such a structure, the thickness, the material, and the sound velocity of the pipe, a region R to be inspected, and the reference waveform are input to the waveform generation/analysis unit 15. The waveform of the reception wave (reception waveform) when the guide wave according to the reference waveform is reflected on a defect Do at the center of the region R to be inspected and is received at the guide wave transceiver 11 is calculated based on the thickness and the material. Transmission waveforms are generated so that the calculated reception waveforms can be transmitted in order from the late reception time.
The guide wave transceiver unit 13 applies a signal based on the transmission waveform to the guide wave transceiver 11 to generate the guide wave 18. The guide wave transceiver unit 13 receives the reception waveform of the guide wave 18 from the guide wave transceiver 11. The A/D converter 14 converts the signal into a digital signal. The waveform generation/analysis unit 15 displays the digital signal on the display unit 17 as an inspection result.
The pipe corrosion can be roughly divided into two types. One is called general corrosion, in which the inside of the pipe is uniformly corroded due to the flowing fluid and the wall of a pipe (hereinafter, also referred to as a pipe wall) is reduced in thickness uniformly. This corrosion often appears in a carbon steel pipe or the like. For the general corrosion, for example, an ultrasonic thickness meter is set at any point on the tube. The appropriate countermeasure can be taken by recognizing the thickness measured with the ultrasonic thickness meter as the thickness of the entire pipe wall.
The other type of the pipe corrosion is called localized corrosion in which the thickness reduction (pitting) or damage progresses locally. The corrosion often appears in a stainless steel pipe or the like. The localized corrosion can be detected when the corrosion has occurred in the place where the ultrasonic thickness meter is set. However, it is impossible to detect the localized corrosion that has occurred in a generation place different from the place where the ultrasonic thickness meter is set.